1. Field of the Invention
The present invention relates in general to automotive air conditioners, and more particularly to the automotive air conditioners of a type that has a bi-level mode wherein conditioned air is blown out from both a ventilation air blow opening and a foot air blow opening at the same time. More specifically, the present invention is concerned with the automotive air conditioners that, under bi-level mode, can provide an air mixing chamber thereof with a unique mixing between cooled air and warmed air thereby permitting the ventilation air blow opening to blow out an air mass having a desired temperature.
2. Description of Related Art
In order to clarify the task of the present invention, one automotive air conditioner of a related art will be briefly described with reference to FIG. 10 of the accompanying drawings.
The automotive air conditioner 100 shown in the drawing is of the type having a bi-level mode, which comprises a unit case 101. Within the unit case 101, there are installed an evaporator 102, a heater 103 and an air mix door unit 104 which is arranged between the evaporator 102 and the heater 103.
The air mix door unit 104 is constructed to have a heater side passage 105 which allows air to flow from the evaporator 102 toward the heater 103, a bypass passage 106 which allows air to flow from the evaporator 102 directly to an air mix chamber 108, and an air distribution slide door 107 which distributes air from the evaporator 102 to the heater side passage 105 and bypass passage 106 at a controlled rate. A warmed air passage 113 extends from the heater 103 to the air mix chamber 108. Thus, under the bi-level mode of the air conditioner 100, in the air mix chamber 108, cooled air flowing from the evaporator through the bypass passage 106 and warmed air from the heater 103 through the warmed air passage 113 are mixed at a controlled ratio thereby to produce a temperature-controlled air in the air mix chamber 108. From the air mix chamber 103, there extend a ventilation air passage 109 and a foot air passage 110. Usually, the ventilation air passage 109 has outlets facing a vertically middle zone of a passenger room and the foot air passage 110 has outlets facing a lower zone of the passenger room. The ventilation and foot air passages 109 and 110 are equipped with pivoting control doors 111 and 112 respectively. Thus, by controlling the working angle of the control doors 111 and 112, a controlled amount of temperature-controlled air is blown into the passenger room from each of the outlets of the passages 109 and 110. The control door 112 is arranged and constructed to distribute the temperature-controlled air in the air mix chamber 108 to both the ventilation and foot air passages 109 and 110 at a controlled rate. For this controlling, the control door 112 pivots between a first position to close the foot air passage 110 while opening the ventilation air passage 109 and a second position to close the ventilation air passage 109 while opening the foot air passage 110. Under the bi-level mode, the control door 112 takes a halfway position between the first and second positions as shown. Thus, under this condition, the temperature-controlled air in the air mix chamber 108 can be led to both the ventilation and foot air passages 109 and 110.
However, due to an inherent construction, the air conditioner 100 has the following weak point. That is, as is seen from FIG. 4A of the accompanying drawings, under the bi-level mode, the control door 112 largely projects into the air mix chamber 108 as shown. Under such condition, cooled air from the evaporator 102 through the bypass passage 106 and warmed air from the heater 103 through the warmed air passage 113 are not effectively mixed in the air mix chamber 108 due to obstruction by the largely projected control door 112. In fact, due to such incomplete mixing in the air mix chamber 108, the ventilation air passage 109 tends to intake air mass whose temperature is cooler than a desired temperature and the foot air passage 110 tends to intake air mass whose temperature is higher than a desired temperature. This means that air blown into the passenger room from the ventilation air passage 109 and air blown into the passenger room from the foot air passage 110 have a remarkable temperature difference, which makes the passengers uncomfortable. This phenomenon becomes much severe when the size of the air mix chamber 108 is reduced.